a) Field of the Invention
This invention relates to ionizing air guns or nozzles in which a high velocity stream of air is directed over an ionizing emitter electrode to expel an ionized stream of air toward a target area to effect static neutralization of charged particles and removal thereof from the targeted surface. More particularly, this invention relates to an ionizing air gun which employs a compressed gas for discharging a high velocity stream of ionized air against a surface in order to neutralize and blast charged particles from a selected area.
b) Prior Art
In prior U.S. Pat. Nos. 3,156,847 and No. 3,179,849, there is shown and described ionizing air guns or nozzles in which an A.C. high voltage generator or power supply is connected directly or capacitively across a pointed needle electrode coaxially disposed within the nozzle of the gun's barrel. A stream of air from a compressed air line is directed through the nozzle parallel with the needle axis and becomes ionized in its passage through the conically radiating high voltage field. Since the air stream reinforces the pattern of the ioning field, an extended range of ionized air is delivered from the nozzle so as be highly effective both in dislodging particles clinging to a surface by electrostatic attraction and in neutralizing charges on the particles and/or on the surfaces preventing reattraction.
In the above cited prior art as well as in the patent art set forth below, compressed air or gas from a cylinder or tank is utilized as the source for expelling the high velocity air through the nozzles:
______________________________________ Patentee U.S. Pat. No. ______________________________________ MOULDEN 4,333,123 LARIGALDIE 4,417,293 SAURENMAN 4,498,116 BLITSHTEYN 4,665,462 CUMMING 4,834,297 ______________________________________
c) Objectives of This Invention
Ion emitter points by virtue of the high voltage imposed on them and because of their geometric configuration tend to attract dust from the atmosphere. The dust is electrostatically attracted to and collects on the sharp tip of the ion emitter point due to the high electric field required for the ionization process. The dust typically collects as a small sphere on the pointed tip, which as it accumulates interferes with the ionization process. When sufficient dust has accumulated, ionization will cease since the point is no longer effectively sharp to cause breakdown of the air dielectric.
Existing devices typically mount the ion emitter point directly in the jet of compressed air. Since compressed air usually contains contaminants, such as water, oil and dirt, the emitter point when directly exposed to such contaminants becomes itself contaminated and dirty. Such contaminants tend to accumulate as a film on these ionizing elements and often lead to conductive paths causing fouling that reduces high voltage or produce arcing, degradation and burn-out. If the emitter point is mounted aside the jet of compressed air, the velocity of the air flowing over the point is insufficient to clean off dust electrostatically attracted to the point, consequently requiring such maintenance as brushing to keep the point clean.
It is therefore an object of this invention to avoid exposure of the ion emitter point to potentially contaminated compressed air streams.
Another object of this invention is to provide an ionizing air gun which will steer the compressed air in a path forward of the emitter point and draw in ambient air from the rear thereof over said point at a velocity high enough to keep said point clean.
Still another object of this invention is to provide a self-cleaning ionizing air gun wherein a plurality of circumferentially spaced compressed air jets are directed in a conical pattern in front of the pointed emitter electrode to draw high velocity ambient over said emitter electrode from the rear of the gun so as to scour accumulated dust therefrom and expel ionized air from the forward end.
Other objects of this invention are to provide an improved device of the character described which is easily and economically produced, sturdy in construction and highly efficient and effective in operation.